Method and apparatus for guidance and actuation of flat belt drive under external load

ABSTRACT

A flat belt drive is trained around spaced apart drive and idler rollers. The belt has an outer load bearing surface and an inner surface wetted to reduce friction on the inner surface where the load is applied. Drainage channels or grooves in the exterior surface of the drive and idler rollers function to remove liquid from between the rollers and the inner surface of the belt in order to maintain a high frictional coefficient therebetween. Alternatively, drainage openings are provided in the roller to convey the liquid away from the roller surface to the hollow interior thereof.

BACKGROUND OF THE INVENTION

The present invention is directed to a method and apparatus for guidanceand actuation of a flat belt drive having an outer load carrying sideand an inner driven side which is wetted and which is trained around adrive and idler rollers.

Such belt drives are used in tire test machines (DE-OS 31 05 163) andparticularly in vehicle test stands or chassis dynamometers (DE-OS 30 40355) designed as so-called flat track test stands.

Unlike chassis dynamometers having rollers closely spaced to oneanother, in the case of flat track test stands, the vehicles are notsupported by the rollers of the dynamometer. Instead, the vehicle orcomponent to be investigated is supported by its wheels which rest upona drive belt wrapped around two rollers or sheaves. In order to assurethat accurate measured values are obtained it is important to make thebelt drive quite stiff in the area of tire contact. As disclosed inDE-OS 31 05 103, this is accomplished at the support arrangement for thedrive belts of tire test machines, by means of a support arrangementlocated between the rollers about which the flat belt is trained. Thisarrangement is covered by a plate with holes out of which liquid emergesperpendicular to the transport direction of the belt drive. The liquidenters the gap between the flexible steel belt and the plate. With thismechanism friction between the steel belt and the necessary supportarrangement is reduced to a minimum, and additionally a stiff guidanceis provided for the drive belt in the area of the tire contact of thewheel to be investigated.

Liquid between the idler and drive rollers and the steel band with theload thereon causes reduction of friction and impairment of guidance. Inorder to prevent the formation of a liquid layer at the steel band whichwould act as a layer between the band and the idler and the driverollers, a wiper of synthetic material is arranged at the end of thesupport arrangement as viewed in the transport direction.

In order not to unreasonably shorten the life of the steel belts whichare subject to constant bending around the drive and idler means it isnecessary to employ large rollers for such belt drives. Further, beltdrives with such rollers have the disadvantage of requiring considerablespace. Their large mass is especially disadvantageous if, by means ofsuch an arrangement, movements in the vertical direction are to betransmitted to the vehicle wheels.

In above mentioned DE-OS 30 40 355 a test stand is disclosed for thedetermination of the fatigue strength of motor cars or chassiscomponents by means of a simulation of service loads. The wheels of themotor car or chassis components to be tested are supported by a rollerelement that is capable of either driving or braking. A separate rollerelement is coordinated to each wheel, and the positions of those rollerelements are adjustable and independent of the position of the otherroller elements. The roller elements in this case consist of linkedbelts that revolve over a load carrying plate between toothed deflectiondrives. An arrangement of this kind is not suitable for investigation athigh speed where considerable forces are exerted because of the highwear rate of the metal parts used.

SUMMARY OF THE INVENTION

One object of the present invention is to achieve a frictionalcoefficient between the inner drive side of an endless flat belt and adrive roller which is practically equal to dry conditions even when thedrive side of such endless belt is wetted. Through proper drainage ofthe drive and idler rollers, the formation of a liquid film is avoided,for example, a liquid film between the outer circumference of a driveroller or an idler roller and the inner drive side of a belt. Drainageoccurs because the flat belt is pretensioned by being wrapped around therollers and as such the belt pushes the liquid to the side within thearea of a draining system.

Through an arrangement of drainage construction, the absorptioncapability of which is at least equal to the amount of liquid thatemanates per unit time from the wetted belt drive, practically the samecoefficient of friction is achieved between the drive and idler rollersand the belt as is obtained with a dry belt drive. The invention makespossible for the first time, the use of drive bands made of syntheticmaterials or rubber in addition to traditional steel bands. Theadvantage of synthetic materials and rubber is that drive and idlerrollers may be used having much smaller diameters than those requiredfor steel bands. Because of the reduction of the mass to be acceleratedand/or decelerated in simulated service tests as well as because of theconsiderably smaller diameters, such test stands can now also be usedfor high speed investigations on vehicles as for instance described inDE-OS 30 40 355. Investigations on individual wheels with verticaldisplacements can now be carried out without having to accelerateunreasonably large masses.

The present invention includes means for the guidance and actuation of aflat belt drive loaded on its outer load carrying side, wetted on itsinner driven side and trained around drive and idler rollers. Throughthe inventive provision of longitudinal profiles or grooves, essentiallylocated in the direction of rotation, on the circumferences of therollers and/or sheaves, which may consist of solid material or may bebuilt hollow as drums, rotating drainage channels are created into whichthe liquid film can escape.

In accordance with the present invention, the volume between the beltand a drainage channel is at least equal to the average liquid volume tobe drained. Such simple means provides the possibility of pushing theliquid film away into the drainage channels while the drive band ismoving around the drive and idler rollers.

Through suitable design of grooves on the surface of the rollers and theroller surface portions therebetween contour fashioned so that theresulting edge pressure is smaller than the shear stress of the materialchosen for the band drive, the service of life of bands made from steel,non-ferrous metals, rubber or synthetic materials, is not adverselyaffected. Especially favorable contours for the roller surface portionsformed between the drainage grooves have resulted from crowned shapeswith rounded edges toward the sides of the grooves.

An arrangement of passageways in the roller interconnecting the drainagechannels or grooves functions to transport liquid to the outside inthose cases where a large stream of liquid occurs that cannot beaccommodated by the drainage channels alone.

A still further modification of the invention involves coordination ofthe load carrying portion of the roller surface portions that engage theflat belt to the distribution of the band tension over the width of therollers. Better preservation of the band material results. It is alsopossible to distribute the drainage channels asymmetrically over thewidth of the drive and idler rollers.

To avoid the possibility of the occurrence of wear marks or nip pointson the drive side of the flat band drive, it is suggested to arrange thedrainage channels sinusoidally in the direction of rotation of therollers.

To avoid fatigue fractures which could result from certain drainagechannels and could lead to breakdown of such band drives in testmachines, it is suggested that the bottom of the channels be fashionedin a rounded manner. A still further modification of the inventionincludes the arrangement of radial holes in the channel bottom of thedrive and idler rollers if they are hollow, and stationary wiper deviceswith liquid diverters connected to them. If an increased liquid volumeoccurs, the excessive liquid volume can escape to the inside and beguided away. The above is particularly applicable in cases where suctionis used for the liquid diversion.

Through the application of smooth drive and idler rollers havingradially directed holes on the surface thereof and through stationaryliquid wipers arranged at the inside of the rollers that cover theroller width and through connected liquid diverters, the liquid layerthat is present on the inner drive side of the band is pushed away intothese holes as the inner drive side of the band runs onto the surface ofthe drive and idler rollers. A favorable coefficient of friction ismaintained between the dry and the wetted drive band and the drive andidler rollers. Beyond this, with such a drive system according to theinvention it is not necessary to carry out additional measures withrespect to changes in the liquid layer and with respect to shearstrength.

The volume of drainage holes over the width of the roller may be thesame or larger than the arriving volume of liquid. Liquid is transportedthrough these holes into the inner portion of the roller. In a stillfurther modification of the invention, the holes of a subsequent row inthe direction of rotation are not located on the same circumferentialcircle but offset thereto between two holes of the preceding row. Thisprevents the formation of a liquid wedge between the holes even at highcircumferential velocities which might otherwise lead to reduction ofthe coefficient of friction between the band and the roller surfaces.

If the holes are countersunk from the outside of the surface area of theroller and the edges of these countersunk holes form web-likeprotrusions, then a network of small webs is created that eliminate anyeventually remaining liquid layer as a result of the pretension of theband drive. There is no need to consider the shear strength of thematerial since the lateral surfaces of the rollers support the driveside of the band, whereby the openings of the network consist ofrecesses, namely the countersunk holes, through which the liquid isguided to the inside of the hollow roller.

Cylindrically countersunk holes represent a special variation of suchcountersunk holes. Instead of cylindrical countersinking, the largestarea of the countersink can also be quadratic, rombic or hexagonal, sothat a corresponding network of small but equally sized load carryingwebs is formed on the surface area of the drive and idler rollers. Thepresent invention may be applied to all rollers such as the, sheaves ordrums of band drives independent of the lateral surface thereof, whethersmooth or crowned.

In cases where rubber or synthetic materials are used for such banddrives, the layer of synthetic material normally applied to the plate ofthe support arrangement between the drive and idler rollers and neededfor emergency operation, can be omitted. The lateral guides by rolls orsupport plates may also be omitted.

BRIEF DESCRIPTION OF THE DRAWING

Novel features and advantages of the present invention in addition tothose mentioned above will become apparent to those of ordinary skill inthe art from a reading of the following detailed description inconnection with the accompanying drawing wherein similar referencecharacters refer to similar parts and in which:

FIG. 1 is a side elevational view of a belt drive illustratingcircumferential drainage channels or grooves in the drive and idlerrollers, according to the present invention;

FIG. 2 is a sectional view taken along line 2--2 of FIG. 1 and alsoillustrating an alternative crowned roller surface which is shown inphantom outline;

FIG. 3 is a partial top plan view of one of the rollers of FIG. 1 withthe circumferential drainage channels or grooves therein;

FIG. 4 is a partial top plan view similar to FIG. 3 but illustrating avariation of the drainage channels or grooves;

FIG. 5 is a partial sectional view similar to FIG. 2 but illustratingalternate drainage channels or grooves;

FIG. 6 is a partial sectional view similar to FIG. 5 but illustratingstill another embodiment;

FIG. 7 is a partial sectional view similar to FIG. 5 but illustratinganother embodiment;

FIG. 8 is a side elevational view of another belt drive illustratingcountersunk drainage openings in the drive and idler rollers, accordingto the present invention;

FIG. 9 is a partial top plan view of the countersunk drainage openingsshown in FIG. 8;

FIG. 10 is a sectional view taken along line 10--10 of FIG. 9;

FIG. 11 is a view similar to FIG. 9 but illustrating differentcountersunk drainage openings;

FIG. 12 is a view similar to FIG. 9 but illustrating still anothervariation of the drainage openings; and

FIG. 13 is a view similar to FIG. 9 illustrating still another variationof the drainage openings.

DETAILED DESCRIPTION OF THE INVENTION

Referring in more particularity to the drawing, FIG. 1 shows a banddrive 3 comprising a drive roller 1 and an idler roller 2 with a flatbelt 4 trained around the rollers 1 and 2. The band drive 3 alsoincludes a support arrangement 5 positioned between the idler roller andthe drive roller for supporting the flat belt 4 particularly when a loadis placed on the outer load bearing surface 8 of the belt. A liquid flow6 emanates from the support arrangement 5, and the liquid flows betweenthe underside of the belt 4 and the support arrangement 5 to provide afluid support against the load of a vehicle wheel 9 acting against theouter load carrying surface 8 of the belt.

The belt 4 is driven so that it moves in the direction of arrow 10,which may either be accomplished by the drive roller 1 but also by thevehicle wheel, and may be in an accelerating as well as in adecelerating mode. Forces act upon the load carrying side 8 of the belt4, and at least part of the liquid stream 6 emanates from a gap 12between belt 4 and support 5 in the direction of arrow 10 to wet theinner drive side 7 of the belt 4 up to the point where the belt contactsthe drive or idler roller. The drive and idler rollers may be hollow orsolid or sheave-like in construction.

Depending on the velocity of the belt 4, the liquid stream 6 tends to bedrawn in the form of a liquid wedge 13 between the surface area of theidler or drive roller and the drive belt 4. This liquid wedge tends toreduce the coefficient of friction between the driven side 7 of the flatbelt 4 and the surface area of the idler or drive rollers. Atcorrespondingly high velocities the coefficient of friction diminishesso much that little if any drive forces for acceleration or decelerationare transmitted between the rollers and the drive surface 7. Under thesecircumstances the lateral forces that are introduced into the loadcarrying side 8 of the drive band 4 are not reacted by roller 1 via thedrive side 7 of the belt 4.

Through an arrangement of drainage channels or grooves 23 formed in theouter surface of the idler and drive rollers, the action of a liquidwedge 13 is suppressed even at high speed.

FIG. 2 shows the cross-section of a drive or idler roller 20 the outsidesurface of which may be of generally cylindrical form 21 or of crownedform 22 upon which drainage channels or grooves 23 are arranged runningin the direction of rotation of the roller.

FIG. 3 shows part of the surface 30 of the drive or idler roller wherethe drainage channels or grooves run parallel to one another in acircumferential direction on the outer surface of the roller. FIG. 4shows an alternative arrangement where the surface 30 has anapproximately sinusoidal course 31 of drainage channels or grooves 23 onthe circumference of the drive or idler roller.

FIG. 5 shows a plurality of drainage channels or grooves 24 each havinga generally rectangular cross-section. In FIG. 6 the drainage grooveseach have a rounded groove bottom 25. FIG. 6 also shows webs 22 betweenthe grooves having the rounded groove bottoms 25. The grooves areinterconnected by passageways 28 which extend in an axial directiondirectly below the roller surface. Radially extending passageways runinwardly for carrying away excess liquid from the area of the drainagechannels or grooves when an excess volume of liquid must be removed.

FIG. 7 shows crowned web surfaces 27 and rounded transitions 29 betweenthose surfaces and the sides 30 of the drainage channels. A displacementof the liquid volume coming from the drive side 7 of the belt 4 isachieved, and, simultaneously, the rounded transition 29 reduces theshear forces that act upon the belt as a result of the pretension of thebelt and the wheel load thereon.

FIG. 8 shows an alternate embodiment including a drive roller 50 andidler roller 52 about which flat belt 4 is trained. Movement of the beltis in the direction of double arrow 11 and at least part of the liquidstream 6 emanates from the gap 14 tending to form a liquid wedge 13 inthe area of the entry of drive band 4 upon the outer surface of thedrive or idler roller. However, these rollers include a plurality ofdrainage openings 15 arranged in the roller surface 16 to drain liquidaway from the roller surface and thereby prevent the formation of anysuch liquid wedge. Also, by means of a wiper arrangement 17 and astationary diverting device 18, draining liquid is removed from insidethe drive and idler rollers. The liquid diversion can, in addition, beenhanced by suction connected to the channels 19. The amount of liquidpulled away by suction may be carried away via the bearing of the smoothdrum when the journals of rollers are formed as hollow shafts.

FIGS. 9 through 13 illustrate different drainage openings for the driveand idler rollers 50, 52. FIGS. 9 and 10 show the radial drainage holes15 of the embodiment of FIG. 8. These openings are surrounded bysquare-shaped countersunk depressions 33. The depressions 33 form asquare pattern of webs 34 which covers the surface of the smoothperforated rollers 50, 52. FIG. 9 shows that the rows of radial holes 15can also be arranged either in a consistent sequence or in a staggeredsequence.

FIG. 11 shows a round web pattern 35, and in this case the radialdrainage openings or holes 15 are surrounded by circular countersunkdepressions 36.

FIG. 12 represents a rombic web pattern 37 which covers the surface ofthe smooth perforated rollers 50, 52 while in FIG. 13 a hexagonal webpattern 38 covers the smooth rollers.

FIG. 10 clearly shows that the flat belt 4 clings to the smoothperforated roller. In this manner, the liquid volume that adheres to theunderside of the belt is forced into the interior of the smoothperforated roller via the square-shaped countersunk portions 33 that areseparated in each case by the web pattern 34 and through the radialholes 15. Wiper devices 17 and diverter devices 18 function to removeliquid from inside the roller.

Through prudent selection of the web pattern a specific web form can beselected for the particular material used for the flat drive belt 4.Proper selection will insure the transmittal of forces between the driveroller 50 and the drive belt 4 for longitudinal as well as for lateralforces, even when the inner surface of the flat belt 4 is covered with aliquid film.

What is claimed is:
 1. A method for guiding and moving a flat belthaving inner and outer surfaces and trained around a drive roller and anidler roller comprising the steps of applying a load to the outer loadcarrying surface of the flat belt, supporting the load from the innersurface of the flat belt, introducing a liquid flow onto the innersurface of the flat belt at the location where the load is applied toassist in supporting the load and to reduce friction, and drainingliquid away from between the flat belt and drive and idler rollers inorder to increase frictional engagement between the flat belt and therollers.
 2. A method as in claim 1 wherein liquid is drained away frombetween the flat belt and drive and idler rollers at a rate equal to therate the liquid is introduced.
 3. Apparatus for guiding and moving abelt comprising a drive roller, an idler roller, and a flat belt trainedaround the rollers, the flat belt having an outer load bearing surfacewhich is flat and an inner flat surface, means for introducing a liquidflow onto the inner flat surface of the flat belt to assist insupporting a load and to reduce friction, and each of the rollers havinga plurality of spaced apart grooves in the exterior surface thereofextending in the direction of rotation of the rollers for drainingliquid from between the belt and the rollers.
 4. Apparatus as in claim 3wherein the grooves in each roller define a volume at least equal tovolume of introduced liquid.
 5. Apparatus as in claim 3 wherein theexterior surface of each roller includes portions between the groovesthat engage the inner surface of the flat belt, each of these rollersurface portions having a crowned contour whereby liquid between theseportions and the inner surface of the flat belt is forced into theadjacent grooves.
 6. Apparatus as in claim 5 including a plurality ofaxially oriented passageways interconnecting adjacent grooves, thepassageways being located directly below the roller surface portionsbetween the grooves.
 7. Apparatus as in claim 3 wherein the grooves areparallel to one another and circumferentially arranged.
 8. Apparatus asin claim 3 wherein the grooves are asymmetrically positioned over thewidth of each roller.
 9. Apparatus as in claim 3 wherein the grooveseach have a sinusoidal configuration in the direction of rotation of therollers.
 10. Apparatus as in claim 3 wherein each of the grooves has abottom surface which is rounded.
 11. Apparatus as in claim 3 whereineach of the rollers includes a plurality of radially oriented drainagepassageways extending inwardly from the grooves.